#!/usr/bin/env python3
"""Packs an image as Argonaut .cor (counterpart of cor2png.py).

The image is converted to 640x480 RGB and compressed with the game's LZ
scheme:
  n < 0x80           -> n bytes of raw data follow (n = 1..127)
  1LLL oooo oooooooo -> copy L+3 bytes (3..10) from o bytes (1..4095) back
Usage: png2cor.py input.png output.cor   (requires Pillow)
"""
import struct
import sys

MAGIC = bytes.fromhex('1798af89fe42d112')
MAXOFF, MINLEN, MAXLEN = 0x0FFF, 3, 10


def pack(raw):
    out = bytearray()
    lit = bytearray()
    last = {}  # 3-byte prefix -> list of recent positions

    def flush():
        for k in range(0, len(lit), 127):
            part = lit[k:k + 127]
            out.append(len(part))
            out.extend(part)
        lit.clear()

    i, n = 0, len(raw)
    while i < n:
        best_len, best_off = 0, 0
        if i + MINLEN <= n:
            key = raw[i:i + 3]
            for p in reversed(last.get(key, ())):
                off = i - p
                if off > MAXOFF:
                    break
                ln = 3
                while ln < MAXLEN and i + ln < n and raw[p + ln] == raw[i + ln]:
                    ln += 1
                if ln > best_len:
                    best_len, best_off = ln, off
                    if ln == MAXLEN:
                        break
        step = best_len if best_len >= MINLEN else 1
        for j in range(i, min(i + step, n - 2)):
            lst = last.setdefault(raw[j:j + 3], [])
            lst.append(j)
            if len(lst) > 16:
                del lst[0]
        if best_len >= MINLEN:
            flush()
            out.append(0x80 | ((best_len - 3) << 4) | (best_off >> 8))
            out.append(best_off & 0xFF)
            i += best_len
        else:
            lit.append(raw[i])
            i += 1
    flush()
    return MAGIC + struct.pack('<III', 1, len(raw), len(out)) + bytes(out)


if __name__ == '__main__':
    from PIL import Image
    img = Image.open(sys.argv[1]).convert('RGB').resize((640, 480), Image.LANCZOS)
    data = pack(img.tobytes())
    open(sys.argv[2], 'wb').write(data)
    print(f'{sys.argv[2]}: {len(data)} bytes')